It is generally well known to treat various edible oils and fats to remove objectionable color or flavors. For example, U.S. Pat. No. 692,283 discloses the removal of color impurities with powdered animal charcoal by mixing such charcoal with fish oil, olive oil and the like which are typically used for dietetic or medicinal purposes. In Bailey's Industrial Oil and Fat Product. Swern, pp.771-77 (1964), various materials such as clay, activated clay, activated carbon are taught as useful in bleaching oils. In particular, Swern teaches using carbon in an amount of about 0.2% to the oil. The use of carbon is preferably always with a bleaching earth. Further, the activity of an adsorbent can be measured by the Freundlich constant,.sup.1 K, the value of which in the examples given varies between 0.25 and 7.2 (with a mean of 1.48) for most active adsorption bleaching processes.
Freundlich equation Kc.sup.n =x/m where x=the amount of substance adsorbed, m=amount of adsorbent, c=amount of residual substance and K and n are constants.
Other processes for improving or enhancing edible and nonedible oils are known in the art. See, for example, U.S. Pat. Nos. 4,112,129 (reducing free fatty acid and color degradation in cooking oils); 3, 450,541 (separating sterols from a liquid mixture); 2,418,819 (removal of water and soaps from oil or fat by percolation); 3,519,435 (fractionation of milk fat); 4,443,379 (adsorptive bleaching of edible oils using Group VIII metal cations and bleaching clays); and 4,005,228 (milk fat crystallization using an acetone solution). Also, PCT application GB82/00327 (method for refining fats using organic solution with adsorption agent).
A number of processes have been directed to the reduction of cholesterol in egg products, for example, U.S. Pat. Nos. 3,987,212; 3,941,892 and 3,563,765. However, few, if any, processes have been successful in reducing or eliminating sterols such as cholesterol in milk fats and like products. In Belgium patent 862,264, however, a method for reducing the cholesterol content of butter by using molecular vacuum distillation is disclosed. It is reported that initial cholesterol content can be reduced by 70-90% using this method.
Granulated carbon processes have been used with dairy products to remove antibiotics or residues from milk, rancidity, and for acid hydrolysis and purification of lactose in whey. The action of bleaching earths on cholesterol was reported in Alteration of Sterol by Industrial Processing of Fats and Oils. by E. Homberg, Fette, Seifen, Anstrichmittel v.76 pp.433-35 (1974). The report focuses on the formation of cholesterol derivatives during the treatment with active earth.
Notwithstanding the dietary advantages in reducing or eliminating cholesterol and its derivatives and other sterols from milk fat products, there have been few processes which provide for large commercial scale removal. Moreover, it is desirable to reduce such cholesterols in fats in such a way as to leave a product useful for the production of edible processed foods.